This invention relates to lenses and more particularly to lenses having specific transmission properties that increase visual acruity and reduce ultraviolet and blue light hazards.
There is a growing awareness that wavelengths of sunlight are harmful to the eye. For example, light of the color blue, more more accurately stated, light with wavelengths between 400 nm and 515  520 nm are harmful over a long period of time. This is a rather surprising conclusion in view of the widespread presence of blue light, for example in the sky. However, tests have shown that blue light does gradually destroy the supply of visual purple which the retina of the human eye possesses, and can lead to senile macular degeneration, night blindness and snow blindness among other problems.
The adverse effects of light having wavelengths in the region between 400-515  520 nm are only recently beginning to be fully recognized and at least partially understood. For many years, persons in the outdoors have attempted to protect their eyes with xe2x80x9cdark glassesxe2x80x9d, and such glasses, often called xe2x80x9csun glassesxe2x80x9d have come in many colors, and with many explanations of their functions. Still, with only a few exceptions, such as special lenses for welders and skiers and filters for cameras and scientific purposes, their effort has been more to reduce the intensity of light transmitted, rather than to filter out any particular wavelength or group of wavelengths.
The special lenses which have existed have severely limited properties, because they are made of glass, and additives for the purpose of modifying the transmissivity and must be compatible with the high temperatures used to make the glass. The range of properties of such substances is very narrow, and does not approach the versatility of organic dyestuffs for this purpose. However, such dyestuffs are destroyed by the temperatures used in making the glass. Accordingly, while glass interference coated filters and lenses with special transmissive properties do exist, they are usually quite costly, and fail to provide the advantages of this invention as to low cost, and to versatility and breadth of function and beneficial effect.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention however, the following patents were considered related:
The Krumeich patent is primarily directed to correcting impaired color vision with lenses having a selective transmission function. The patent limits transmission in the blue range while allowing almost complete transmission in the red range. As can be seen in FIG. 1 of the patent, wavelengths less than about 490 nm are substantially cut-off having about 0.01% transmission. Light having wavelengths of about 550 nm or longer has at least about 10% transmission. Additionally, light having wavelengths of about 600 nm or longer has at least a 70% transmission.
The Miller patent discloses a glass composition that has improved ultraviolet and infrared transmittance characteristics. The invention is especially useful in manufacturing lenses for housing infrared and ultra-violet or radio-frequency detectors as are used in missile systems.
The Bush patent discloses selective color filtration devices for underwater viewing or photography. The patent discloses a predetermined color-selective light-filtering coating on a light source that is used for underwater viewing or photography. For example, to absorb light in the blue-green end of the visible spectrum and to pass the red, orange and yellow wavelengths, in accordance with a predetermined formula, the coating corrects to some extent the filtering effect caused by the water and by the particles suspended in the water. By following the teachings of the present invention, underwater objects may be photographed in more natural colors, and without the usual bluish-greenish tinge which normally accompanys objects that are photographed by present day equipment.
The Francel, et al patent discloses a method for coating a vitreous substrate with a fluid coating composition. The coating imparts to an otherwise clear and/or transparent glass substrate the light transmittance characteristics of an amber glass. Amber glass, which is widely used for a variety of applications such as reflectors, insulators and glass containers, inherently screens out appreciable percentages of lightwaves in the visible spectrum. For example, at 400 nm, the range of light transmission is between 1.53-7.0%; at 450 nm between 3.5-16.0%; and at 500 nm between 7.0-27.0%.
The lens of the instant invention is made of a plastic material into which is incorporated an organic orange dye 3. This dye has the property of allowing the lens to transmit at least 90% of the visible sunlight with wavelengths longer than 636  600 nm and block more than 99% of all sunlight with wavelengths shorter than 515  520 nm.
The inventive lens are designed to improve visual acuity and to specifically eliminate ultraviolet (uv) and reduce blue light hazard.
The elimination of uv radiation can help avoid cataractogenisis, better known as cataracts; and the reduction of blue light can help avoid senile mascular degeneration which is especially prevalent in humans having outdoor occupations.
The lens is also designed to improve visual acuity in a bright sunlit environment by blocking the following photons:
violet and blue light that is preferentially scattered by atmospheric particles;
violet and blue light that is preferentially scattered by particles within the vitreous humor of the eye;
violet and blue light that is focused in front of the retina by the simple lens of the eye;
violet and blue light during the day that preferentially bleaches the Rhodopson in the rod structure of the retina thus reducing night vision;
ultraviolet radiation that causes the lens and vitreous humor of the eye to fluores and reduce the scene contrast that is projected onto the retina.
In view of the above disclosure, it is the primary object of the invention to provide a lens that is worn in front of the eyes by humans in an outdoor, sunlit environment. The lenses provide a filter barrier to photons that are deleterious to the eyes.
A further object of the invention is to provide a lens that transmits visible light most useful for high visual acuity in brightly sunlit environment.
An additional object of the invention is to provide a choice of sharp cut-on filtering lenses within the narrow range of 35 nm.
Still another object of the invention is to have that can be manufactured in the form of a spectacle lens or a contact lens.
These and other objects and advantages of the present invention will become apparent from the subsequent detailed description of the preferred embodiment and the appended claims taken in conjunction with the accompanying drawings.